The invention concerns a coupling configuration comprising a coupling element and a supply capillary, wherein the coupling element has a funnel-shaped section which clamps an end of the supply capillary.
A coupling means of this type is disclosed in the catalogue of Polymicro Technologies, LLC, PT-MLC/03-02, “Inner-Lok” of 2002.
Capillaries (supply capillaries) are used to supply liquid samples to a measuring apparatus, e.g. a gas chromatography system or an NMR spectrometer. These capillaries are usually produced from fused silica to ensure good chemical resistance of the capillary to the test sample or its solvent. The sample is thereby mostly pushed along by a downstream transport liquid, e.g. pure solvent. The capillaries have a relatively small inner diameter, in most cases in a range below 0.5 mm, in order to also be able to supply small sample amounts.
The construction of a transition from one capillary to another capillary, or another means to which the liquid test sample is to be supplied, is thereby particularly difficult to realize. The capillary is conventionally fixed, e.g. melted, at such transition locations. Mounting is generally quite expensive and time-consuming, and moreover susceptible to damage. If the capillary is damaged, e.g. broken, it must be repaired by experts, which is expensive.
In contrast thereto, so-called “press fit” connections or couplings are very easy to mount. A capillary is thereby inserted into a cone of a coupling element and pressed through the tapering. This type of clamping fixation, which is based on the elastic properties of the capillary, is sufficiently rigid for many applications.
The above-mentioned “inner-lok” is substantially a glass tube whose inner diameter decreases from both openings towards the inside. One capillary can be pushed into each opening, whereby two capillaries can be connected to each other.
This type of mounting, however, bears the danger that the capillary is not sufficiently fixed in the coupling element and might be inadvertently removed from the coupling element. Damage to a capillary, in particular breakage in the vicinity of the coupling element, could also easily happen.
It is therefore the underlying purpose of the present invention to provide a coupling configuration of the above-mentioned type, wherein mounting of the supply capillary in the coupling element is improved, as is protection against capillary breakage.